Cannot push more than one documents to collection (11000) - mongodb

Question

This is my Operation Model:
const mongoose = require('mongoose');
const operationSchema = mongoose.Schema({
user: {
type: mongoose.Schema.Types.ObjectId,
ref: 'User'
},
extract: {
type: mongoose.Schema.Types.ObjectId,
ref: 'Extract'
},
normalizations: [{
type: mongoose.Schema.Types.ObjectId,
ref: 'Normalize'
}],
ingestions: [{
type: mongoose.Schema.Types.ObjectId,
ref: 'Ingest'
}]
});
module.exports = mongoose.model('Operation', operationSchema);
This is how I am creating an Operation:
exports.create = async (req, res, nexr) => {
let op = new Operation
op.user = mongoose.Types.ObjectId(req.body.user);
op.extract = mongoose.Types.ObjectId(req.body.extract);
op.normalizations = [];
op.ingestions = [];
const operation = new Operation(op);
try {
await operation.save();
console.log(operation)
res.send(operation);
} catch (err) {
console.log(operation)
res.status(500).send(err);
}
}
NO UNIQUE LABELS exists in any of the User, Extract, Normalize, Ingest Models
When I try to push to Mongo, the first time everything is ok.
If I try to push more than one records I get this error from Postman:
{
"driver": true,
"name": "MongoError",
"index": 0,
"code": 11000,
"keyPattern": {
"extract.name": 1
},
"keyValue": {
"extract.name": null
} }

Answer 1

only a single document in the collection can be missing the unique field.There is already a document in this collection with a missing or null value. The index is not present in the collection in which you are trying to insert. So try this, drop that collection from the database and run the program again.
Any documents missing the source_references.key field will be considered as having a null value. If you want the index to only apply to documents with a source_references.key field you can use sparse:true index creation option.